It would be helpful to post a link to your sources.
However, the article I link to below is a good (and long) study on the firmament, and includes various theories and approaches:
Considerable disagreement exists in the church about what God made on the second day of Creation Week in Genesis 1.
answersresearchjournal.org
The fact remains though, that our modern knowledge of
reality completely falsifies the notion of a solid dome over the earth. If you want to try to convince me of such, you will have to show me an independent expedition where somebody flies a rocket to the very dome, extends a robotic arm to touch it, scrapes a piece off, brings it back to earth to be independently examined, and includes photographs and video footage of everything, including of a flat disc earth below. Only then will I consider the earth not being a globe and the firmament being solid. Because all other evidence is against such a notion.
How do we know Jesus wasn't speaking literally when He said He is a door, vine, bread or shepherd? Because the reality proves He was not being literal. It's the same with the "firmament". How do we know it's not solid? Because the reality proves it's not solid.
However, as
@tharkun73 has pointed out, Scripture tells us that the sun moon and stars move
in the firmament. And the sun moves differently to the moon, and both move differently to the stars. And the "wandering stars" (planets) move differently to all of them. If these are
in the firmament as the Bible says, then the firmament cannot be solid.
You have shown on a different thread that you only take the words of Scripture literally when it suits you. For instance, you claim this verse is literal:
"
And the sun stood still, and the moon stayed, until the people had avenged themselves upon their enemies. Is not this written in the book of Jasher? So the sun stood still in the midst of heaven, and hasted not to go down about a whole day." Joshua 10:13 KJV
But you don't take this verse literally:
"
And when the sun was going down, a deep sleep fell upon Abram; and, lo, an horror of great darkness fell upon him." Genesis 15:12 KJV
You have said that the sun "appears to" go down, but that it's actually traveling further away. That's a serious inconsistency on your part.
People have pointed out to you that the sun stopping in Joshua was what it "appeared to" do to the people seeing it. And you tried to pass that off as nonsense. But now you have done the same thing. That's not just inconsistency, it's being hypocritical.